Method of manufacturing a rigid internal gear of a wave gear device

Abstract

A rigid internal gear 2 of the wave gear device is composed by integrating a tooth-forming ring 12 formed with internal teeth, and a main gear ring 11 into a single body. The tooth-forming ring 12 is manufactured from a ferrous or copper material that has superior strength and abrasion resistance, while the main gear ring 11 is manufactured from a lightweight material, such as an aluminum alloy. The outer circumferential surface of the tooth-forming ring 12 is aluminized to form a dispersed aluminum coating 15, before the tooth-forming ring 12 is cast within the main gear ring 11 so as to integrate the main gear ring 11 and the tooth-forming ring 12. Both parts are reliably integrated so that a large amount of torque can be transmitted, whereby realizing a rigid internal gear that is lighter than conventional models.

1. A method of manufacturing a rigid internal gear of a wave gear device, in which the rigid internal gear comprises a main gear ring and a tooth-forming ring having internal teeth formed on an inner circumferential surface thereof and, in which the tooth-forming ring is disclosed inside the main gear body and integrally bonded thereto,
 the method comprising steps of:  
 forming the main gear ring from a first material that has a first linear expansion coefficient;  
 forming the tooth-forming ring from a second material that has a second linear expansion coefficient; and  
 pressing the tooth-forming ring into an inside of the main gear ring and diffusion-combining the tooth-forming ring and the main gear ring;  
 wherein the first linear expansion coefficient is lower than the second linear expansion coefficient.  
 
   
   
     2. A method of manufacturing a rigid internal gear according to  claim 1 ,
 wherein the first material is a titanium alloy with a linear expansion coefficient of approximately 8.8×10 −6 , and  
 the second material is a ferrous material with a linear expansion coefficient of approximately 12.0×10 −6 .  
 
   
   
     3. A method of manufacturing a rigid internal gear according to  claim 1 ,
 wherein the first material is a ceramic material with a linear expansion coefficient of approximately 7.8×10 −6 , and  
 the second material is a stainless steel material with a linear expansion coefficient of approximately 17.0×10 −6 .  
 
   
   
     4. A method of manufacturing a rigid internal gear according to  claim 1 ,
 wherein the first material is an aluminum alloy with a linear expansion coefficient in a range of 6.2×10 −6  to 10.0×10 −6 , and  
 the second material is an aluminum alloy with a linear expansion coefficient in a range of 20×10 −6  to 24×10 −6 .  
 
   
   
     5. A method of manufacturing a rigid internal gear according to  claim 1 , wherein an inner circumferential surface of the main gear ring is tapered,
 an outer circumferential surface of the tooth-forming ring is tapered that the tooth-forming ring can be pressed into the tapered inner circumferential surface of the main gear ring, and  
 the tooth-forming ring is pressed onto the inner circumferential surface of the main gear ring and the tooth-forming ring and main gear ring are diffusion-bonded together.  
 
   
   
     6. A method of manufacturing a rigid internal gear according to  claim 1 , wherein a gear cutting process for forming the internal teeth on the tooth-forming ring is performed after the tooth-forming ring has been joined to the main gear ring to form a single body. 
   
   
     7. A rigid internal gear of a wave gear device manufactured by a method of manufacturing according to  claim 1 .